Subaru GLF Back Up Light Bulb Size

The Subaru GLF back up light requires bulb size 1156 or P21W depending on the specific version of the vehicle. Data for the bulb size covers the range from 1980 to 1982.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1980-1982	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

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Additional Notes

The 1156 is the sole bulb type listed across all model years of the Subaru GLF back up light application covered by these specifications, spanning 1980-1982.
The 1156 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical standards shared across North American markets.
It operates on a 12-volt system and draws 21 watts, which is consistent with standard automotive electrical systems of that era.
The 1156 uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin, distinguishing it from the dual-contact BA15d variant used in other applications.
As a single-filament bulb, the 1156 serves one dedicated function per socket, which aligns with its use in a back up light role rather than a combined stop/tail application.
The BA15s base type is a widely produced standard, meaning the 1156 is broadly available as a replacement across automotive supply channels.
Substituting a dual-contact bayonet bulb, such as a 1157, into a BA15s socket is not possible without modification, as the base configurations are physically incompatible.